This invention is directed towards a paper feeding apparatus, and more particularly to a paper feeding apparatus for use with a printer.
A conventional paper feeding apparatus is driven by a motor. The motor may also power a platen of a printer or be dedicated to powering only the paper feeding apparatus. FIG. 13 illustrates a device 100 in which a printer 150 has a motor (not shown) which drives both a platen (i.e. printing cylinder) 104 and a paper feeding apparatus 160. Device 100 is disclosed in a Japanese Patent Publication No. 58-6633 published on Feb. 5, 1983; U.S. Pat. No. 4,248,419 is equivalent thereto. Device 100 also includes a paper separation roller 105 and a paper feed-out roller 106. A transmission mechanism (not shown) couples the rotational force of platen 104 to paper separation roller 105 for feeding a top sheet from a stack of papers 121 to platen 104. The transmission mechanism also couples the rotational force of platen 104 to paper feed-out roller 106 for advancing the top sheet beyond a print head 109 and discharging it into a storage section 107.
The stack of papers 121 is loaded into a hopper 101 of paper feeding apparatus 160 by placing the stack on a pressure plate 103. A spring 129 biases pressure plate 103 towards paper feeding roller 105. As platen 104 rotates in a counterclockwise direction, paper feed roller 105 rotates in a clockwise direction and grabs through frictional contact a top sheet 121A from stack of papers 121. A corner of top sheet 121A, which is initially disposed under and pressed against a separation claw 108 of hopper body 101, is dragged over separation claw 108 by paper feeding roller 105. As feed roller 105 continues to rotate, top sheet 121A is released from hopper 101 and advanced by feed roller 105 until in contact with platen 104. Platen 104 now switches directions rotating in a clockwise direction to advance the top sheet between platen 104 and print head 109 for printing by the latter. The top sheet is thereafter discharged into storage section 107 by paper feed-out roller 106.
Conventional paper feeding mechanisms such as apparatus 160 cannot use a single separation device (i.e. separation claw 108) for separating relatively thin paper, envelopes and postcards stacked within hopper 101. Each type of recording medium requires a separating mechanism exclusively for use with that type of recording medium. When a recording medium different from the recording medium presently loaded in apparatus 160 is to be fed into printer 150, the present separating mechanism will either be detached from apparatus 160 and replaced with a new separating mechanism or have additional elements added thereto.
Apparatus 160 also requires a predetermined minimum distance between paper feed roller 105 and platen 104. The distance is equal to the length of the smallest size sheet of paper to be fed into platen 104. Paper having a length less than this minimum distance (e.g. a slip of paper) cannot be adequately advanced by paper feed roller 105 to be properly fed into platen 104. Apparatus 160 also includes a tractor 622 having sprockets (not shown) to feed fanfold paper (e.g. computer paper) into printer 150. Storage section 107, however, is too small to hold the fanfold paper.
The angle at which the sheet 121A from the stack of papers 121 contacts separation claw 108 changes as the height of the stack decreases due to pressure plate 103 rotating about a shaft 102. A space (i.e. gap) between claw 108 and the top sheet is created when the height of the stack drops below a certain level. Individual sheets from the stack of papers 121 are no longer individually removed by paper feed roller 105. Instead, platen 104 attempts to advance more than one sheet at a time through printer 150. Wrinkling and/or other deformation of the sheets and/or jamming of printer 150 can result.
It is therefore desirable to provide a paper feeding apparatus which can feed different lengths of recording media into the platen of the printer, which can accommodate fanfold paper and which prevents the feeding of more than one sheet of paper into the platen no matter how depleted the stack of papers may be within the hopper. Preferably, the paper feeding apparatus should feed sheets of paper into the platen having lengths as short as about 80 millimeters. No additional or different attachments should be required for feeding individual sheets of paper, envelopes, postcards or the like into the platen.